连续流双污泥系统反硝化除磷实验研究

通过实验室小试,以生活污水为研究对象考察了厌氧/缺氧与淹没式好氧生物膜滤床相结合的连续流双污泥系统的除磷脱氮效果.长期试验结果表明,该工艺解决了传统脱氮除磷工艺中反硝化菌与聚磷菌竞争碳源这一主要矛盾,并可以分别控制硝化污泥与反硝化聚磷污泥的污泥龄,而且该系统适合处理C/N较低的生活污水,与传统除磷脱氮工艺相比,不用额外投加碳源,剩余污泥含磷量高,节省曝气量.系统对COD、总磷、总氮和氨氮的平均去除率分别为81.78%、92.51%、75.75%和84.47%.     

反硝化除磷污泥系统驯化及其性能影响因素研究综述

传统生物脱氮除磷工艺存在碳源竞争、溶解氧需求大和菌群结构竞争等诸多问题,反硝化同步脱氮除磷能够在缺氧条件下以硝酸盐为电子受体,在脱氮的同时进行超量聚磷,实现氮磷同步去除,具有节约碳源、能源、污泥产量低等优点,符合污水处理工艺节能减排的绿色发展理念.反硝化聚磷污泥的驯化是运行反硝化同步脱氮除磷工艺的前提,文中综述了一步法...     

SUFR脱氮除磷系统中反硝化聚磷菌的性能研究

对螺旋升流式反应器(SUFR)脱氮除磷系统中高PHB及低PHB含量的污泥在有无外碳源及硝酸盐条件下的反硝化吸磷／释磷性能进行了试验研究。结果表明：(1)反硝化聚磷菌约占全部聚磷菌总量的72．4％,同时加入碳源和磷酸盐的反硝化速率高于只加入碳源的反硝化速率,约有37％～39％的脱氮作用是由反硝化聚磷菌完成的;(2)当有外碳源存在时,反硝化速率是无外碳源时的1.6倍左右,PHB含量高的污泥表现出反硝化吸磷现象,PHB含量低的污泥表现出反硝化释磷现象;(3)在缺氧条件下,吸磷量与消耗PHB的比值为0．71～0．86,低于在好氧条件下的1．08。     

序批式反应器中反硝化除磷脱氮的研究

为了提高污水脱氮除磷的效率,研究采用序批式反应器(SBR工艺)厌氧、好氧和缺氧(AOA)的运行方式富集反硝化聚磷菌(DPB),实现同步脱氮除磷。结果表明:在好氧段投加甲醇作为碳源(25—40 mg/L)可有效抑制好氧吸磷,对硝化反应影响较小,能够在缺氧段实现同时反硝化脱氮除磷。SBR反应器稳定运行10个月,当进水NH4+-N、PO43--P分别为30,15 mg/L时,总氮(TN)和PO43--P的平均去除率分别为82.5%和92.1%。聚磷菌能够利用硝酸盐作为电子受体,DPB占总聚磷菌的比例达到44.8%。与A2O运行方式相比,AOA运行方式更有利于实现DPB的富集。     

A2ON工艺反硝化除磷机理及影响因素

活性污泥法与生物膜法相结合,基于反硝化除磷原理,开发出双污泥序批式脱氮除磷处理工艺A2ON.作者重点研究了生活污水COD/TN比值变化对其除磷脱氮性能的影响.试验结果表明,稳定运行的反应器具有良好的强化生物除磷和反硝化脱氮性能,缺氧结束时体系中磷＜1 ms/L,氮＜5 mg/L.该工艺处理效果稳定,对水质的适应能力强,可以降低好氧需求,较大程度地减少除磷和反硝化对碳源的竞争,同时保证了世代时间长的硝化菌的稳定生长.     

反硝化聚磷菌脱氮除磷机理研究

目前水体中氮磷含量较高的问题逐渐严重,利用反硝化聚磷菌来进行脱氮除磷的反硝化除磷工艺为生物脱氮除磷提供了新的方向。本研究以反硝化聚磷机理为基础,采用动态的SBR反应器进行菌种的富集培养,驯化富集反硝化聚磷菌,同时跟踪富集过程中污染物的去除情况。实验结果表明,富集成功后SBR系统内除磷率达到80%以上,总氮及COD的去除率达到90%左右,系统稳定且脱氮除磷效果较好。通过吸磷实验、反硝化脱氮产气实验从富集的活性污泥中,筛选出来4株反硝化聚磷菌。     

AOA工艺内源反硝化强化深度脱氮除磷

以实际低C/N生活污水为处理对象,考察了AOA（厌氧/好氧/缺氧）工艺内源反硝化脱氮除磷性能。实验重点研究了生物填料的快速挂膜情况、微生物种群结构变化和系统脱氮除磷效率。结果表明,接种污泥后系统污染物去除性能迅速提高,阶段Ⅲ出水COD、NH₄+^-N、TIN、TP平均浓度分别为33.36 mg/L、1.80 mg/L、5.27 mg/L和0.23 mg/L,相应的去除率分别77.4%、94.6%、84.3%和94.2%。FISH实验结果表明,活性污泥中功能菌聚糖菌GAOs占比13.5%,聚磷菌PAOs占比11.1%,生物膜上硝化菌AOB占比18.3%,NOB占比9.2%。在无外加碳源条件下,系统利用原水内碳源通过后置内源反硝化和反硝化除磷实现深度脱氮除磷,同时AOA工艺只有污泥回流,较传统A²O工艺节省了硝化液回流能耗,运维管理方便。     

水解反硝化工艺强化脱氮处理

碳源对脱氮除磷都具有重要的作用,碳源不足会导致脱氮效果降低,出水TN水质不达标。为解决碳源不足造成的脱氮能力差的问题,本试验采用水解反硝化脱氮工艺,将水解酸化与反硝化脱氮过程相结合,取代缺氧反硝化,有效地解决了碳源不足所导致的脱氮效果差的问题。利用水解反硝化脱氮工艺处理城市污水,出水NH₄⁺-N、TN和COD都满足一级A标准,去除率分别为98.0%、69.4%和82.7%,比同期污水处理厂AAO工艺的TN去除率高出17.5%。在BOD₅/TN为3～5的条件下,水解池中污泥的比反硝化速率为缺氧池污泥的1.2～1.7倍,并且去除相同的N所需要的碳源较少,在碳氮比为3:1、3.5:1、4:1和5:1时去除单位N水解池可分别节省59.5%、52.2%、19.9%和23.1%的COD,有效地解决了脱氮过程中碳源不足问题。     

餐厨垃圾污泥共发酵强化低C/N A2O脱氮除磷

为寻求餐厨垃圾污泥资源化利用方式,明晰共发酵产酸对厌氧-缺氧-好氧(A~2O)工艺脱氮除磷强化效果。研究共发酵产酸对强化生物反硝化可行性,对比研究传统碳源和发酵液对A2O工艺脱氮除磷性能的影响,并解析该过程的微生物群落特性。结果表明,采用餐饮垃圾和污泥共发酵产物可作为生物脱氮除磷碳源,反硝化效率为5.31mg/(g·h);与甲醇作为碳源相比,发酵液对NH_4~+-N和TP的去除效果分别提高2.04和4.84百分点;而对TN的去除差别较小。采用不同的碳源,活性污泥中微生物群落组成发生显著差别,发酵液作为碳源优势菌群为Rhodocyclaceae。     

长泥龄改良A2/O工艺的短程硝化反硝化除磷

为解决传统A²/O工艺硝化与除磷泥龄(SRT)之间的矛盾,进一步提高低C/N(P)比生活污水同步脱氮除磷效率,采用一种改良A²/O工艺在长SRT条件下处理生活污水.试验结果表明,该工艺可有效筛选和强化反应器内活性污泥,并大量富集长SRT的反硝化除磷菌(DPAO).通过亚硝酸盐氧化菌(NOB)淘洗阶段后,反应器在SRT=19.6d、A²O段污泥浓度(MLSS)=5.5 g·L^-1、水力停留时间(HRT)=8.2 h、污泥回流比(R)=90%、硝化液回流比(r)=250%、溶解氧(DO)=1.5～0.3 mg·L^-1,间歇曝气段HRT=4 h、曝气周期1 h曝气1 min(DO=0.3～0.5 mg·L^-1)、沉淀59 min条件下长期运行,COD、NH₄⁺-N、TP和TN的平均去除率分别为88.71%、99.2%、93.77%和89.52%,出水亚硝化率(NO₂^--N/NO_x^--N)可达97.2%,DPAO占聚磷菌(PAO)比为95.5%.污水中约72.96%的COD被DPAO合成PHA除磷,15.75%的COD由异养反硝化消耗,约41.96%和31.31%的N分别通过反硝化除磷和异养反硝化去除.剩余污泥主要由DPAO和反硝化菌增殖产生,分别占82.74%和17.24%,较传统脱氮除磷途径减少了58.76%的碳源消耗和44.6%的污泥排放.     

欧盟公布染料化学名称

该文根据欧盟2000年公布的第五版和2002年公布的第六版《欧洲化学物质申报清单》，选择一些重要的染料品种，介绍了他们的化学名称，以及可供参考的结构式。     

An efficient method for creation and functional analysis of libraries of hybrid type I polyketide synthases

Bacterial type I polyketide synthases (PKSs) generate a structurally diverse group of natural products with a wide range of biological activities. Hybrid type I PKSs in which domains of one multifunctional polypeptide are replaced with components from heterologous systems have generated significant interest over the past decade. Almost invariably only one or several specific hybrids are made at a time and tested for functionality. This approach is slow, dependent upon a fortuitous choice of specific fusions points, and often leads to inactive or minimally active hybrid systems. We describe herein a method for generating and screening a library of hybrid pikAI complementation plasmids (encoding the loading domain and the first two extension domains of pikromycin PKS) able to restore pikromycin in a BB138 Streptomyces venezuelae pikAI-deletion mutant. In the first step the plasmid sequence encoding the loading domain AT(0)-ACP(0) was replaced by a counter selectable marker, sacB. DNA family shuffling was then used to generate a diverse library of chimeric AT(0)-ACP(0) fragments, which were used to replace sacB by lambda-Red-mediated in vivo recombination in an Escherichia coli host. This method resulted in the rapid and efficient generation of a large number of hybrid pikAI complementation plasmids, which were used to transform S.venezuelae BB138. A bioassay of over 4000 of these transformants successfully revealed three different PikAI hybrids which were able to lead to pikromycin production. The study suggests that most of the hybrids are not detectably functional, and underscores the need to generate and screen large and diverse libraries in which different fusion points are tried. The methodologies applied in this study address this need and can be used for directed evolution of any component of the PikPKS, and potentially other type I PKS systems.     

Effect of protein fusion on the transition temperature of an environmentally responsive elastin-like polypeptide: a role for surface hydrophobicity?

The limited throughput, scalability and high cost of protein purification by chromatography provide motivation for the development of non-chromatographic protein purification technologies that are cheaper and easier to implement in a high-throughput format for proteomics applications and to scale up for industrial bioprocessing. We have shown that genetic fusion of a recombinant protein to an elastin-like polypeptide (ELP) imparts the environmentally sensitive solubility property of the ELP to the fusion protein, and thereby allows selective separation of the fusion protein from Escherichia coli lysate by aggregation above a critical temperature (T(t)). Further development of ELP fusion proteins as widely applicable purification tools necessitates a quantitative understanding of how fused proteins perturb the ELP T(t) such that purification conditions (T(t)) may be predicted a priori for new recombinant proteins. We report here the effect that fusing six different proteins has on the T(t) of an ELP. A negative correlation between T(t) and the fraction hydrophobic surface area on the fused proteins was observed, which was determined from computer modeling of the available three-dimensional structure. The thermally triggered aggregation behavior of ELP-coated, functionalized gold colloids as well as ligand binding to the tendamistat-ELP fusion protein support the hypothesis that hydrophobic surfaces in molecular proximity to ELPs depress the ELP T(t) by a mechanism analogous to hydrophobic residue substitution in the ELP repeat, Val-Pro-Gly-Xaa-Gly.     

Determination of Algerian Hassi-Messaoud asphaltene aromaticity with different solid-state NMR sequences

Algerian oil well deposit derived asphaltene fraction was characterized by different MAS/NMR sequences to investigate asphaltene aromaticity and the best cross-polarization contact time. The aromaticity was estimated by single pulse sequence (SP), Hahn-echo (HE), cross-polarization (CP) and variable cross-polarization (VACP) sequences. The values found ranging from 0.58 to 0.48 are of the same order of magnitude as ones published in the literature. The discrepancies between the values are thought to be relevant to both the specificity of each sequence and the asphaltene structure. Spectra band de-convolution enables us the determination of the average number of carbon atoms per side chain according to each sequence. The obtained values spanning from 3 to 7 are also sequence nature dependent.     

A novel emulsion mixture for in vitro compartmentalization of transcription and translation in the rabbit reticulocyte system

Emulsion formulations used for in vitro compartmentalization (IVC) methods were found to be incompatible with protein expression in the rabbit reticulocyte (RRL) system, causing rapid discoloration and translation shutdown. Here we identify possible causes and describe a novel water-in-oil emulsion which abolished discoloration and allowed high-level in-emulsion expression of active luciferase and human telomerase using the RRL. This novel emulsion greatly expands the range of potential protein targets for IVC.     

Conservation and covariance in PH domain sequences: physicochemical profile and information theoretical analysis of XLA-causing mutations in the Btk PH domain

Mutations that cause X-linked agammaglobulinemia (XLA) appear throughout the Bruton tyrosine kinase (Btk) sequence, including the pleckstrin homology (PH) domain. To analyze the basis of this disease with respect to protein structure, we studied the relationships between PH domain sequences and structures by comparing sequence-based profiles of physicochemical properties and solvent accessibility profiles. The diversity of the distribution of amino acids was measured by calculating entropies for sequences containing mutations at different positions in multiple sequence alignments. Mutual information was calculated to quantify positional covariation. Eight conserved extrema were apparent in all profiles. The majority of the XLA disease-causing mutations in the Btk PH domain were found at positions having significant mutual information, indicating that there are covariant constraints for both structure and function. Together with additional structural analyses, all the XLA mutations that were analyzed could be explained at the molecular level. The method developed here is applicable to the design of mutations for protein engineering.     

Identification of potent human anti-IL-1RI antagonist antibodies

Interleukin-1 (IL-1) blockade by IL-1 receptor antagonist benefits some arthritis patients by reducing joint damage. This fact inspired us to develop antagonist human therapeutic antibodies against IL-1R(I) using phage libraries that display single-chain variable fragment (scFv) antibody fragments. Panning libraries against human IL-1R(I) generated 39 unique scFv-phage whose binding to IL-1R(I) was competed by IL-1 ligands. Fifteen of these scFv-phage, identified using IL-1R(I)-binding assays and dissociation rate ranking, were reformatted as scFv-Fc and IgG(4) molecules. The ease of producing antibodies in the scFv-Fc format permitted rapid identification of four lead clones (C10, C13, C14, C15) that inhibit NF-kappaB nuclear translocation induced by IL-1. Reformatting these clones as IgG(4) molecules increased their inhibition potency by 相似文献   

Fusion of the antiferritin antibody VL domain to barnase results in enhanced solubility and altered pH stability

Chimeric immunotoxins that combine antigen recognition domains of antibodies and cytotoxic RNases have attracted much attention in recent years as potential targeted agents for cancer immunotherapy. In an attempt to obtain a structurally minimized immunofusion for folding/stability studies, we constructed the chimeric protein VL-barnase. The chimera comprises a small cytotoxic enzyme barnase, ribonuclease from Bacillus amyloliquefaciens, fused to the C-terminus of the light chain variable domain (VL) of the anti-human ferritin monoclonal antibody F11. While the individual VL domain was expressed in Escherichia coli as insoluble protein packed into inclusion bodies, its fusion to barnase resulted in a significant ( approximately 70%) fraction of soluble protein, with only a minor insoluble fraction ( approximately 30%) packed into inclusion bodies. The in vivo solubilizing effect of barnase was also observed in vitro and suggests a chaperone-like role that barnase exerted with regard to the N-terminal VL domain. Cytoplasmic VL-barnase was analyzed for structural and functional properties. The dimeric state of the chimeric protein was demonstrated by size-exclusion chromatography, thus indicating that fusion to barnase did not abrogate the intrinsic dimerization propensity of the VL domain. Ferritin-binding affinity and specificity in terms of constants of association with isoferritins were identical for the isolated VL domain and its barnase fusion, and RNase activity remained unchanged after the fusion. Intrinsic fluorescence spectra showed a fully compact tertiary structure of the fusion protein. However, significantly altered pH stability of the fusion protein versus individual VL and barnase was shown by the pH-induced changes in both intrinsic fluorescence and binding of ANS. Together, the results indicate that VL-barnase retained the antigen-binding affinity, specificity and RNase activity pertinent to the two individual constituents, and that their fusion into a single-chain chimeric protein resulted in an altered tertiary fold and pH stability.     

A cell-based screen for function of the four-helix bundle protein Rop: a new tool for combinatorial experiments in biophysics

Combinatorial methodologies have revolutionized studies in biomolecular function, but they have so far proven less useful for understanding macromolecular structure and stability. This is largely because of the difficulty of screening libraries of molecules for biophysical properties, and the difficulty of interpreting structural effects in complicated molecules. Here, we report a novel, robust, cell-based screen for function of the four-helix bundle protein, Rop. By expression of green fluorescent protein from a ColE1 plasmid, the screen reports the copy number of the plasmid, which is modulated in Escherichia coli by Rop. We have engineered the screen so that the fluorescent phenotype can correspond to either Rop activity or lack thereof. We have used the screen to demonstrate with systematically constructed Rop core variants that not all molecules that bind small stem-loop RNAs in vitro are active in vivo. Rop is well understood from structural work and systematic mutations, which makes it possible to construct rational, targeted libraries. This screen makes it possible to rapidly interrogate such libraries effectively for proper protein folding and stability. In addition to its intended utility for combinatorial experiments in biophysics, the screen will allow further dissection of the mechanism of Rop-mediated plasmid copy number regulation in vivo.